1. Field of the Invention
This invention relates generally to a method and apparatus for shear testing of bonding materials for objects such as ceramic tiles, and more particularly, to an apparatus and method for in-place testing of a tile bonded to a working surface.
2. Description of the Related Art
A number of shear testing devices are known in the art. Some prior art patents disclose a method and apparatus for shear testing bonding material on a test piece or article which has been removed for such purpose from its working position. Examples are U.S. Pat. Nos. 2,353,056 to Martindell; 2,667,781 and 2,674,124 to Barrett; 3,376,736 to Emery, Jr.; 3,026,721 to Ensor et al.; and 2,675,699 to Tilden.
U.S. Pat. No. 2,667,781 to Barrett relates to an apparatus for testing a shear strength of a bond of a brake lining adhesively bonded to a brake shoe. A bonded brake shoe is set on supporting surfaces adjacent a U-shaped slot designed to receive a portion of the brake shoe, with one edge-face of the shoe abutted against a shoulder. Air pressure is then applied to a chamber, which pushes a diaphragm and attached ram forward, resisted by a tension spring. A serrated pressure applying element at a forwardly projecting end of the ram is advanced against a second edge-face of the brake lining until shearing occurs.
In a known device for bench testing the shear strength of a bond holding a tile to a surface, two test tile portions are bonded together with a bonding joint such that the two tiles are offset from one another. One tile is placed into engagement with a portion of the frame of the apparatus, and an opposite edge of the second tile engages a piston actuated by a hydraulic cylinder. The piston forces one tile toward the other until shearing of the bond occurs. A pressure gauge is provided for measuring the pressure in the hydraulic cylinder corresponding to the shearing force applied.
The primary disadvantages with these prior apparatus are the inconvenience involved in preparing the test pieces and the inaccuracy resulting from bench testing rather than testing on an actual working surface.
In U.S. Pat. No. 3,090,252 to Hollar et al., a test button on a panel is prepared in the skin of the panel by removing material in an annular region around the button to a depth of the thickness of the skin. An adaptor is placed against an edge of the test button and shears the test button when actuated. A pressure-actuated piston presses against a load arm to which the adaptor is attached. The load arm pivots about a pin in an upper portion of a frame, and forces the adaptor forward until the test button is sheared.
Although the device of Hollar et al. is used to test the button in place, the load arm which transmits the shearing force to the adaptor does so by pivoting about the pin. The adaptor thus moves through an arc rather than by moving a shearing member in a direction parallel to the panel as with the present invention.
The present invention overcomes the shortcomings of the prior art by providing an apparatus and method for testing a shear strength of a bond of a tile attached to a working surface by applying a force parallel to the working surface.